Re: [Gumstix-users] Re: Revised Robostix Proposal

Hi Sean,
Since I know a bunch of the answers to your questions, I'll answer the
ones I know.
> Further, obtaining housings and pins for female 0.1in connectors is
> generally easy, but I do not believe the same can be said for 2mm. In
> our case, our university's ECE dept. supply shop carries tons of 0.1in
> connectors, but I'm pretty sure they don't carry 2mm. You can also buy
> 0.1in connectors in small quantities from a large number of robotics
> hobby vendors (for example, http://www.botrics.com/products/wirekit/ as
> one of many).
>
> Use male headers (same as the servos).
I agree with your sentiment about the 0.1" I could live with 2mm would
strongly prefer the 0.1" personally, I already have the required
crimper tool and just bought a couple hundred dollars of housings and
pins for 0.1" because I use it so much.
> 1. I'm a CS and not an ECE guy: I can only barely read wiring
> schematics. Could someone summarize the basic features being proposed
> for the Robostix?
>
> - How big is the power regulator?
That isn't clear to me yet. The schematic is inconsistant with
Gordon's statements, so I think that this requires clarification.
> - Is there separate servo power?
Yes. There is 0.1" connector to bring in separate servo power.
> - How many servo outs? What resolution?
There are six PWM outputs, all wired up with Gnd/V+/servo which is
compatible with most servos (some servos use +V+/Gnd/Servo but these
aren't as common).
The PWM's that are available are referred to in the AVR datasheet as
OC1A, OC1B, OC2, OC3A, OC3B, and OC3C. The number in the mnemonic
refers to the timer that the particular OC (Output Compare) is
connected to. Timer 1 and 3 are 16 bit timers, so you could get upto
16 bit resoloution. This really depends on the frequency output you're
looking for. If you require a particular frequency that doesn't
correspond to one of the builtin prescalars, then you can get it but
with reduced resolution. Timer 2 is an 8 bit timer
> - What kinds and number of motor outs? Do they require additional
> hbridges?
There are no HBridges in the current design (and I wouldn't expect
any). You would typically provide your own H-Bridge which matches the
motors you're planning on using and connect it up to some GPIO's for
the direction/enable and the PWM on the servo lines for the speed.
> - Digital outs?
> - Digital ins?
There are 8 PortC pins, which can be configured as input or output.
There are 5 pins on the AT_INTS connectors that can be used as inputs
or outputs.
> - Analog ins? At what voltage range? What resolution?
There are 8 Analog ins. The voltages can be 0-5v and have 10 bit resolution.
> - Specifics of the I2C bus? Can it be in both master or slave? One of
> my students reports that the Gumstix cannot become slave without
> writing a new kernel driver.
The i2c on the AVR can be master or slave, and can run upto 400 kHz.
As it is currently, you are correct that the gumstix doesn't really
support being a slave. I plan on implementing that functionality for
my own robot, so it will be there eventually.
> - To make switches easy, can pull-up resistors be included, creating
> some two-pin connectors?
The AVR has builtin pullup resistors that can be enabled/disabled
individually for each I/O pin. So you would just use the 3 pin
connector with 2 wires connected, one to ground and one to the signal.
> - Reset switch?
Is currently tied to the gumstix.
> - How many RS232 serial ins remain? At least one is _abolutely_
> necessary, and two would be highly desirable to enable hook-up of the
> very popular CMUCam2 or GPS and still be able to log in.
The console on the gumstix would be available via the tweener board.
The IR port on the gumstix is voltage converted on the RoboStix and
brought out to a connector. The 2 UARTs on the AVR are also available.
The way that the connectors are arranged, the IR connector on the
gumstix can easily be jumpered to connect to one of the serial ports
on the AVR.
Since other, faster communciation methods could be used between the
gumstix and the AVR (i2c or SPI) you don't need to jumper the two
serial ports together, but you can.
> - One or two feedback LEDs showing heartbeats etc.?
Currently not there, but would be nice. I noticed that PB4 (aka OC0)
isn't connected to anything. This would make a good choice for an LED
since then you could setup the PWM to drive it and actually vary the
intensity of the LED as well as configuring it on/off
> 2. The diagram appears to have holes on the board for screws on three
> corners, not four, and they're not rectangular (one hole is oddly
> placed). PLEASE have four large holes big enough to allow a standard
> machine screw, organized rectangularly. If the board needs to be
> enlarged in all dimensions slightly to do that, it's still reasonable.
> A way to keep the Gumstix stable as it sits on top (or hangs below)
> would be very helpful as well -- otherwise we'll be resorting to wire
> ties!
To tie down the 4th corner, you could also put a screw beside the
Robotstix with a washer that overhangs. The SMT breakout board has a
hole in the 4th corner, so it should be possible to add too.
--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/

Thread view

MOSI =3D Master Out, Slave In
Opposite for MISO
Makes it easy to remember direction.=20
-----Original Message-----
From: gumstix-users-admin@...
[mailto:gumstix-users-admin@...] On Behalf Of Dave
Hylands
Sent: Friday, February 25, 2005 4:14 PM
To: gumstix-users@...
Subject: [SPAM] - Re: [Gumstix-users] Revised Robostix Proposal - Email
found in subject
> The schematic shows X_MISO connecting to ATM_MISO and X_MOSI=20
> connecting to ATM_MOSI, shouldn't they cross over? i.e. X_MISO to=20
> ATM_MOSI and X_MOSI to ATM_MISO.
Sorry - the schematic is correct. The pins change direction depending on
whether you're a master or a slave.
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0. A strong plea for NOT using 2mm. Though it may seem convenient
spacing-wise to avoid multiple rows, 0.1in header spacing (or at any
rate whatever servos use) is very nearly UNIVERSAL on the controllers I
use. The Handyboard, Brainstem, Cerebellum, and practically every
other hobbiest and small-robot controller on the market are at 0.1. If
you do 2mm, you'll essentially be making yourself pin-incompatible with
them. To entice this crowd to migrate to your board, it's not helpful
to require retooling of our sensors and motors. This is not a small
concern: a lot of organizations (such as KIPR/botball) will make
decisions for their new board when they replace the Handyboard nearly
entirely on how easy it will be to migrate almost a thousand high
schools from one system to the other.
Further, obtaining housings and pins for female 0.1in connectors is
generally easy, but I do not believe the same can be said for 2mm. In
our case, our university's ECE dept. supply shop carries tons of 0.1in
connectors, but I'm pretty sure they don't carry 2mm. You can also buy
0.1in connectors in small quantities from a large number of robotics
hobby vendors (for example, http://www.botrics.com/products/wirekit/ as
one of many).
Use male headers (same as the servos).
1. I'm a CS and not an ECE guy: I can only barely read wiring
schematics. Could someone summarize the basic features being proposed
for the Robostix?
- How big is the power regulator?
- Is there separate servo power?
- How many servo outs? What resolution?
- What kinds and number of motor outs? Do they require additional
hbridges?
- Digital outs?
- Digital ins?
- Analog ins? At what voltage range? What resolution?
- Specifics of the I2C bus? Can it be in both master or slave? One of
my students reports that the Gumstix cannot become slave without
writing a new kernel driver.
- To make switches easy, can pull-up resistors be included, creating
some two-pin connectors?
- Reset switch?
- How many RS232 serial ins remain? At least one is _abolutely_
necessary, and two would be highly desirable to enable hook-up of the
very popular CMUCam2 or GPS and still be able to log in.
- One or two feedback LEDs showing heartbeats etc.?
2. The diagram appears to have holes on the board for screws on three
corners, not four, and they're not rectangular (one hole is oddly
placed). PLEASE have four large holes big enough to allow a standard
machine screw, organized rectangularly. If the board needs to be
enlarged in all dimensions slightly to do that, it's still reasonable.
A way to keep the Gumstix stable as it sits on top (or hangs below)
would be very helpful as well -- otherwise we'll be resorting to wire
ties!
Sean

Hi Sean,
Since I know a bunch of the answers to your questions, I'll answer the
ones I know.
> Further, obtaining housings and pins for female 0.1in connectors is
> generally easy, but I do not believe the same can be said for 2mm. In
> our case, our university's ECE dept. supply shop carries tons of 0.1in
> connectors, but I'm pretty sure they don't carry 2mm. You can also buy
> 0.1in connectors in small quantities from a large number of robotics
> hobby vendors (for example, http://www.botrics.com/products/wirekit/ as
> one of many).
>
> Use male headers (same as the servos).
I agree with your sentiment about the 0.1" I could live with 2mm would
strongly prefer the 0.1" personally, I already have the required
crimper tool and just bought a couple hundred dollars of housings and
pins for 0.1" because I use it so much.
> 1. I'm a CS and not an ECE guy: I can only barely read wiring
> schematics. Could someone summarize the basic features being proposed
> for the Robostix?
>
> - How big is the power regulator?
That isn't clear to me yet. The schematic is inconsistant with
Gordon's statements, so I think that this requires clarification.
> - Is there separate servo power?
Yes. There is 0.1" connector to bring in separate servo power.
> - How many servo outs? What resolution?
There are six PWM outputs, all wired up with Gnd/V+/servo which is
compatible with most servos (some servos use +V+/Gnd/Servo but these
aren't as common).
The PWM's that are available are referred to in the AVR datasheet as
OC1A, OC1B, OC2, OC3A, OC3B, and OC3C. The number in the mnemonic
refers to the timer that the particular OC (Output Compare) is
connected to. Timer 1 and 3 are 16 bit timers, so you could get upto
16 bit resoloution. This really depends on the frequency output you're
looking for. If you require a particular frequency that doesn't
correspond to one of the builtin prescalars, then you can get it but
with reduced resolution. Timer 2 is an 8 bit timer
> - What kinds and number of motor outs? Do they require additional
> hbridges?
There are no HBridges in the current design (and I wouldn't expect
any). You would typically provide your own H-Bridge which matches the
motors you're planning on using and connect it up to some GPIO's for
the direction/enable and the PWM on the servo lines for the speed.
> - Digital outs?
> - Digital ins?
There are 8 PortC pins, which can be configured as input or output.
There are 5 pins on the AT_INTS connectors that can be used as inputs
or outputs.
> - Analog ins? At what voltage range? What resolution?
There are 8 Analog ins. The voltages can be 0-5v and have 10 bit resolution.
> - Specifics of the I2C bus? Can it be in both master or slave? One of
> my students reports that the Gumstix cannot become slave without
> writing a new kernel driver.
The i2c on the AVR can be master or slave, and can run upto 400 kHz.
As it is currently, you are correct that the gumstix doesn't really
support being a slave. I plan on implementing that functionality for
my own robot, so it will be there eventually.
> - To make switches easy, can pull-up resistors be included, creating
> some two-pin connectors?
The AVR has builtin pullup resistors that can be enabled/disabled
individually for each I/O pin. So you would just use the 3 pin
connector with 2 wires connected, one to ground and one to the signal.
> - Reset switch?
Is currently tied to the gumstix.
> - How many RS232 serial ins remain? At least one is _abolutely_
> necessary, and two would be highly desirable to enable hook-up of the
> very popular CMUCam2 or GPS and still be able to log in.
The console on the gumstix would be available via the tweener board.
The IR port on the gumstix is voltage converted on the RoboStix and
brought out to a connector. The 2 UARTs on the AVR are also available.
The way that the connectors are arranged, the IR connector on the
gumstix can easily be jumpered to connect to one of the serial ports
on the AVR.
Since other, faster communciation methods could be used between the
gumstix and the AVR (i2c or SPI) you don't need to jumper the two
serial ports together, but you can.
> - One or two feedback LEDs showing heartbeats etc.?
Currently not there, but would be nice. I noticed that PB4 (aka OC0)
isn't connected to anything. This would make a good choice for an LED
since then you could setup the PWM to drive it and actually vary the
intensity of the LED as well as configuring it on/off
> 2. The diagram appears to have holes on the board for screws on three
> corners, not four, and they're not rectangular (one hole is oddly
> placed). PLEASE have four large holes big enough to allow a standard
> machine screw, organized rectangularly. If the board needs to be
> enlarged in all dimensions slightly to do that, it's still reasonable.
> A way to keep the Gumstix stable as it sits on top (or hangs below)
> would be very helpful as well -- otherwise we'll be resorting to wire
> ties!
To tie down the 4th corner, you could also put a screw beside the
Robotstix with a washer that overhangs. The SMT breakout board has a
hole in the 4th corner, so it should be possible to add too.
--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/